This invention relates generally to power collection systems and more particularly to novel devices for transmitting power from a rigid conductor to electrically driven, rail vehicles.
A customary approach to collecting relatively heavy currents from a rigid conductor for propelling an electrically operated vehicle, such as a locomotive is to utilize a current collector of pantograph type having an articulated lower structure fixed to the roof of the locomotive and friction bands or shoes and their accessories constituting the actual current collector which are generally linear in configuration for the powers concerned. Although the articulated lower structure generally supports the friction bands through a medium of elastic suspension components so as to enable the current collector to remain in contact with the rigid conductor or the catenary during operation, there is a tendency in the pantograph structure of the prior art to move out of engagement with the rigid conductor and thereby interrupt the flow of current therebetween.
This tendency is accentuated with increasing vehicle speed, where, in addition to the increased relative speed between the engaged conductor and collector members, with the attendant propensity for separation, the aerodynamic force acting on the pantograph also begins to affect its disposition with respect to the rigid conductor.
Difficulties encountered are that all catenaries have certain elasticity due to their constructions and profiles which vary from one conductor to another, where it is necessary that the lift produced by the static force applied by the pantograph, is less at the points of suspension of the conductor than at points near the center of the conductor span, and this variation in lift is proportional to the speed of the locomotive.
Various efforts have been made in order to minimize the disadvantages of the variations in pressure and to maintain the static force applied upwardly by the current collector against the rigid conductor constant as possible. However, all these attempts are limited to the improvements concerning known supporting structures generally referred to as pantographs.
The addition of a single or double action shock absorber to the lower structure so that the actual current collector is supported by the lower structure having the low spring constant characteristics, has led to only mediocre results. If properly devised, the low spring constant characteristics will provide for a "soft shoe" which is flexible to the changes in pressure due to said irregularities of the rigid conductor.
However, on the other hand, friction bands or shoes need to be forced against the rigid conductor with respect to the lower structure with a high average force so as to continue to pickup current correctly and to support rigid conductor partially displaced back by said lift.
It is known to increase the static force by a force of aerodynamic origin. The aerodynamic force depends upon the magnitude of the mass of the articulated system. This method, however, has the disadvantage of simultaneously increasing the lift and deformation of the rigid conductor.
Simultaneous accomplishments of actual current collecting without disruption, and supporting the rigid conductor with the current collector of the pantograph type are apparently not expected, since such collector is constructed to have the means for collecting current and the means for supporting said means in series, whereby the art to provide a high average force against the contact conductor for supporting the rigid conductor while retaining the desired low spring constant within the working range for being flexible to the changes in pressure, is substantially not possible.
In a different way, even various modifications, to the conductor concerned have been attempted. Recently, it is found that rigid conductor is so effective for the super high speed locomotive that it is employed as a substitute for the ordinary catenary wire.
However, all of these modifications, even if applied simultaneously, do not permit satisfactory current collection especially for high speed locomotive, as long as the substantial mechanical defects mentioned above of the pantograph type remain.
Recently, increasing public nuisance produced by noise and sparks and a second problem caused by poor current collection and loss of contact accompanied by arcing has become a serious matter to be considered.
In order to minimize the disadvantages mentioned above, although much attention has been given to the improvement of the material used, especially for the actual current collecting portion or the shoe, these materials remain unsuccessful, mainly depending upon the fact that the elastic suspension of the shoe is still too "stiff".
Accordingly, an essential object of the present invention is to provide a current collecting assembly including the art for transmitting power from the rigid conductor to electrically driven, rail vehicles, which can substantially provide an average force against the rigid conductor to support the rigid conductor partially displaced back while retaining the spring constant as low as possible within desired working ranges to properly pick up current.
Another important object of the present invention is to provide a current collecting assembly of the above described type which is accompanied by improvements in the material used for the actual contact portions of said devices to maintain the working duration of said devices as long as possible and to prevent the public nuisance caused by loss of contact between the wire and current collecting assembly.
A further object of the present invention is to provide a current collecting assembly of the above described type accompanied with the above mentioned improvements on the material which are simple to fabricate, ecconomical to operate and extremely functional in use.